This invention relates to a cathodic corrosion prevention system for a marine outboard drive and more particularly to an improved device of this type that embodies electrical power supply for maintaining a pre-determined potential on the marine outboard drive to assist in the cathodic protection.
Marine outboard drives in the forms of outboard motors or the outboard drive portion of an inboard/outboard drive arrangement normally employ outer housings made of light weight alloy such as aluminum alloys or the like. In addition, however, such outboard drives also embody other metals and the resulting difference in metals can give rise to galvanic corrosion of the metal higher on the activity chart.
A variety of electrical protection arrangements have been employed for such outboard drives wherein the outboard drive is supplied with electrical power so as to maintain a desired electrical potential on the outboard drive so as to limit this corrosion. This is done by applying a direct current power source to the outboard drive and to an electrode which is mounted in a spaced position from the outboard drive so as to maintain the desired potential on the outboard drive. The electrode is supplied with current at an amount determined by a reference electrode which, preferably, is mounted in close relationship to the power electrode and spaced substantially at the same distance from the outboard drive as the power electrode so as to maintain the proper current depending upon the nature of the water (fresh or salt) in which the watercraft is operating. These systems can be quite effective.
One disadvantage with this type of system, however, is that the reference electrode will itself deteriorate and dissolve in the body of water in which the watercraft is operating and this will change its signal and can adversely effect the performance of the protection system. In addition, the reference electrode, which normally is formed from a small piece of wire, must be protected from damage by underwater objects.
It is therefore, a principal object to this invention to provide an improved outside power source-type of electrical corrosion protection system for a marine outboard drive.
It is a further object to this invention to provide an improved reference electrode arrangement for such a system wherein it is insured that the reference electrode will have a long life and provide a uniform and consistent signal throughout its life.